import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int x = scanner.nextInt();
        if(x>=90){
            System.out.println('A');
        }else if(x>=80){
            System.out.println('B');
        }else if(x>=70){
            System.out.println('C');
        }else if(x>=60){
            System.out.println('D');
        }else{
            System.out.println('E');
        }
    }
}
